#!/bin/bash
echo "hello,world~"

#test1 define var A

A=100
echo  A =$A

#test2 withdraw var A

unset A
echo  "A=$A "

#test3 call static var B=2,can not unset

readonly B=2
echo "B=$B"
unset B

#test4 backticks to run the program and put the result return 
# to A

A='unset'
A=(unset)
ehco A


#muti-line comments

:<<!
123
!

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